This invention relates to stringed racquets for tennis, squash, racquet ball or the like in which in play a racquet strikes a ball. The invention has particular relationship to stringing of the racquets so as to improve the properties of the racquets in play.
Racquets are commonly strung with tensioned string of natural animal gut or synthetic materials or metal wire. The natural gut is made from beef or lamb intestines, and the synthetic materials are made of polymeric materials such as nylon (polyamides or polymeric composites). Natural gut is normally considered to have better playing characteristics; however, it is more costly, affected by weather, and has a short life. Usually a racquet is strung with one continuous length of string (about 33 feet long in the case of a tennis racquet). The string is subject to the same tension, typically of about 55 pounds, throughout. Typically, the string has a diameter of about 0.040 to 0.060 inch. In some cases two separate string lengths may be used as shorter lengths than the 33 feet are more readily manufactured and with shorter lengths stringing is facilitated for some racquets. However, where a racquet is strung with two lengths of string, both are usually subject to the same tension.
An important factor in playing performance is the area of the "sweet spot" or the center section of the racquet which exhibits a relatively true rebound to the ball. It is desirable that this "sweet spot" be of as large as practicable area as balls struck outside of the "sweet spot" do not bounce truely and there is a fault when a ball is struck in this outside area. In an attempt to enhance the area of the "sweet spot," stringers have strung racquets so that the strings are diagonal or so that there are missing rows of strings near the top, bottom and sides, i.e., around the periphery of the racquet. Neither of these expedients has been sufficiently successful to receive widespread adoption. Stringers have also attempted to string portions of the racquets at different tensions; but, this was not successful because the tensions could not be maintained at the initial desired settings during play.
It is an object of this invention to maximize effectively the area of racquet which manifests relatively true rebound.